To pronounce the upsilon, position your tongue as if to make the sound of the EE in "see", then round out your lips as if to make the sound of the OO in "zoo". The result should sound intermediate between EE and OO.
The chi originally had an aspirated K sound (K + H) but later developed into a fricative. Make like you're going to pronounce the K but put a little bit of space between your tongue and palate so that it makes a hiss.
Accents originally indicated tone: acute = rising, grave = falling, and circumflex = rising then falling. When starting out learning the pronunciation, I found it easier to ignore the distinction and simply stress the indicated syllable; after the pronunciation becomes more natural it gets easier to make a distinction between the different tones.